1. Field of the Invention
This invention relates to sound attenuating mufflers and, more particularly, to sound attenuating mufflers for damping sound waves of various frequencies.
2. Discussion
Automotive mufflers are incorporated in exhaust systems to limit the audible level of sound waves produced as a result of engine operations. Often automotive mufflers are provided with some type of heat resistant fibrous material such as glass, steel wool or a porous ceramic to absorb sound waves. This type of muffler, generally referred to as an absorbent type of muffler typically comprises a pipe perforated with numerous holes for the passage of the gases, and a pipe larger in diameter than the perforated pipe and receiving the latter in its axial bore. The tubular space defined by the inner and outer pipes is filled with the permeable and heat resistant material which serves to absorb the sound waves.
The prior art muffler systems have proven to be relatively ineffective at attenuating sound waves having drastically varying frequencies. Also, because of the arrangement of the porous absorbent material, the absorbent material is apt to break down over time significantly limiting the functionality and life span of the muffler.